The fiber definition file let MSC.Marc talk to MSC.Patran.

The weaved medical device gets implanted in the tongue to stop the effects of sleep apnea.

Results let the implant designers compare how the tongue behaves at a certain time interval while the patient is saying the vowel pattern “i-u,” both with the implant (left) and without it (right).

The constitutive material used for the tongue was implemented via a standard Ogden model. It is a quasi-incompressible, elastomeric model for rubber-type materials which is often used to represent tissue in biomedical simulations. The model defines the stress/ strain curve of a particular tissue. We implemented the muscle activations through the HYPELA2 user subroutine. User subroutines are a vehicle Marc provides which allows advanced solver manipulation through direct Fortran coding.

The final solved models revealed how Genioglossus can be activated along its fanshaped pattern to create motions critical to speech and swallowing. Under the hood, the custom code is inducing internal stresses, which in turn produce forces which ultimately result in macroscopic displacements of the full tongue body. Speech therapists find this model particularly useful because, in reality, it’s impossible to have a subject activate only a single muscle in their tongue. Simulated study of individual muscles, therefore, provides researchers with insight they would not normally have available to them in a standard physical laboratory environment.

The final finite element model contained 13 different muscles that could individually simulate activation through space and time. Such simulations aided in the development of a sleep apnea implant by helping developers understand what happens when someone says a common vowel pattern, such as “i-u”, or makes a swallowing motion, with and without the device. In turn, this helped optimize the device. Tagged MRIs and ultrasounds validated results.

The author acknowledges these key individual in the modeling project:

Maureen Stone, speech scientist at the University of Maryland Dental School, for important data including MRIs from physical studies for test correlation.

Reiner Wilhelms-Tricario from Haskins Laboratories for serving as the mathematician and sharing his knowledge on the different types of mathematical approaches to muscle modeling.

Paul Buscemi, senior director study development at WuXi Apptec, Inc., for adding geometrical tongue definitions.